1. Field of Invention
The present invention relates to an active matrix drive type electro-optical device and an electronic apparatus. Specifically, the invention relates to an electro-optical device having pixel-switching thin film transistors (hereinafter “TFTs”) within a stacked structure, on a substrate and an electronic apparatus, such as a projector, that includes such an electro-optical device.
2. Description of Related Art
In electro-optical devices, such as TFT active matrix drive type liquid crystal devices, EL (Electro-luminescence) display devices and the like, when the incident light is irradiated to a channel region of a pixel-switching TFT provided in each pixel, a light leakage current results from excitation by the light to vary characteristics of the TFT. Specifically, in case of electro-optical devices for a light valve of projectors, since intensity of the incident light is high, it is important to shield the channel region or its adjacent region of the TFT from the incident light.
Therefore, in the related art, in each pixel provided on the counter substrate, by use of a light shielding film to define an opening region reflecting or transmitting the light to be contribute to the a display or by use of data lines extending over a TFT and being made of metal film, such as aluminum (Al), such channel region or its adjacent region is shielded from light. Further, the light shielding film made of, for example, high melting-point metal may be also provided below the pixel-switching TFT on the TFT array substrate. If the light shielding film is also provided below the TFT like above, it is possible to previously prevent the light from entering the TFT of the electro-optical device, where the light may be the back-reflected light from the TFT array substrate side or the return light, such as the projected light which is passed through a prism from other electro-optical device, when a plurality of electro-optical devices are combined through prism to constitute an optical system.
The various light shielding technologies described above are subject to the following problems.
First, according to the technology of forming the light shielding film on the counter substrate or the TFT array substrate, since the light shielding film and the channel region are separated considerably apart from each other through, for example, a liquid crystal layer, an electrode, an interlayer insulating film and the like as viewed three dimensionally, it is not sufficient to prevent the light from entering obliquely between both. Specifically, in a small sized electro-optical device used as light valve of projector, the incident light is a light beam condensing the light from a light source through a lens, and unnegligibly or not insignificantly contains components to be obliquely irradiated. For example, since the incident light may contain 10% of components oblique by 10° to 15° from a direction perpendicular to the substrate, it creates a problem in practice that such oblique incident light is not blocked sufficiently.
Further, the light entering the electro-optical device through a region not having the light shielding film may be reflected from the upper face of the substrate or the light shielding film formed on the substrate or the data line, and then such a reflected light or the multiple reflected light may reach finally the channel region of the TFT. The multiple reflected light is generated by re-reflecting the reflected light from the substrate, the light shielding film or the data line.
Specifically, in order to accomplish the high accuracy of the electro-optical device or the minuteness of pixel pitch due to a recent general requirement of high quality of the displayed image, as the intensity of the incident light is increased to display a brighter image, problems occur, such as it is more difficult to perform the sufficient light shielding by use of the aforementioned related light shielding technologies and the flicker phenomena may be generated due to gradation of the transistor characteristics of TFT, thereby deteriorating quality of the displayed image.
Furthermore, although it may be considered that an area to form the light shielding film should be simply made to be greater in order to increase the lightproof property, there is a problem that it is basically difficult to increase the aperture ratio of each pixel only by use of it and thus the displayed image becomes dark.